如何获取指定窗口的像素点？

[尘埃黎明]

比如已知一个窗口的HWND,如何得到该窗口所有像素RGB的BUFFER?
我用下面这种方法，发现bitmap.bmbits的值为0,怎么回事?
HDC hdcScr = ::GetDC(m_hWnd);
HDC hdcMem = CreateCompatibleDC(hdcScr);
HBITMAP hBmp = CreateCompatibleBitmap(hdcScr, wid, hei);
SelectObject(hdcMem, hBmp);
BITMAP bitmap;
GetObject(hBmp, sizeof(BITMAP), &bitmap);

[bishuiliuyun]

同意BeyondSky007的答案……

[wltg2001]

用GetDIBits试试

[Eleven]

HDC hSrcDC = ::GetWindowDC(hWnd);   
ASSERT(hSrcDC);   
HDC hMemDC = ::CreateCompatibleDC(hSrcDC);   
ASSERT(hMemDC);   
HBITMAP hBitmap = ::CreateCompatibleBitmap(hSrcDC, nWidht, nHeight);   
ASSERT(hBitmap);   
HBITMAP hOldBitmap = (HBITMAP)::SelectObject(hMemDC, hBitmap);   
::BitBlt(hMemDC, 0, 0, nWidht, nHeight, hSrcDC, 0, 0, SRCCOPY);   
BITMAP bitmap = {0};   
::GetObject(hBitmap, sizeof(BITMAP), &bitmap);  

http://blog.csdn.net/VisualEleven/archive/2011/02/23/6202796.aspx

[尘埃黎明]

刚试了一下，这样bitmap的bmbits还是0

[singwhatiwanna]

getpixel

[尘埃黎明]

用getpixel一个点一个点的获取确实可以，但是感觉程序有点卡